Human males have both a X and a Y chromosome but females have two X chromosomes. This means that in an early stage in the development of a woman’s fertilised egg the cells need to silence one of those two X chromosomes. This process is crucial to survival and problems with the process are related to serious genetic diseases.
Both X chromosomes in a cell have a suicide gene called XIST which, if activated, seals the chromosome behind a barrier of RNA preventing the activation of any other gene. Researchers believe that this suicide gene can be itself blocked by a plug of proteins forming on top of its specific location on the chromosome but they had little idea as to why this should happen randomly to one X chromosome’s gene and not the other.
Scientists are extremely uncomfortable with this randomness and have sought a clear scientific reason as to why one X chromosome was switched off rather than the other. The observations also seem to run counter to the usual idea that the biological mechanisms evolve in ways that allow a "best" choice to be made between things rather than a random one.
Now researchers led by University of Warwick physicist Dr Mario Nicodemi have explained how this randomness occurs and why that it is beneficial. This will help understand the problems of a small number of women who unusually don’t have a completely random distribution of X chromosomes but the explanation may have much wider implications as at least 10% of our genes may behave in similar ways as mechanism that "chooses" between X chromosomes. Examples of this range from the immune system to our olfactory apparatus.
Coming at the problem from the perspective of a physicist Dr Nicodemi has found an explanation for the random selection based on thermodynamics. Research has already shown that at the key moment in this process both X chromosomes are brought close together within the cell. The Warwick researcher paper says that what happens next is that material for a "protein plug" then begins to gather around both of the XIST suicide genes on each X Chromosome. This starts a race between the two build ups of protein. Inevitably one of these two nascent protein plugs narrowly wins that race and reaches an energy state in which it can pull together all the material building up in both plugs into a single protein plug. That single plug then closes off one of the XIST suicide genes allowing its host X chromosome to continue to operate. However the other XIST suicide gene is now freed to activate and shuts down its X chromosome.
Since putting forward this explanation researchers in Harvard have observed actual plugs of protein shutting down X chromosome XIST genes in a manner giving further confirmation to Dr Nicodemi’s research. So the randomness is explained but what about researchers’ other concerns? Dr Nicodemi believes the randomness actually does give an evolutionary advantage. The mechanism means equal numbers of both the maternal and paternal X chromosome are preserved in the gene pool and the resultant population thus has more chance of surviving any biological threat targeted at a single version of the X chromosome.
Peter Dunn | alfa
Biologists unravel another mystery of what makes DNA go 'loopy'
16.03.2018 | Emory Health Sciences
Scientists map the portal to the cell's nucleus
16.03.2018 | Rockefeller University
Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...
On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...
The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...
At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.
When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...
At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.
Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...
16.03.2018 | Event News
13.03.2018 | Event News
08.03.2018 | Event News
16.03.2018 | Earth Sciences
16.03.2018 | Physics and Astronomy
16.03.2018 | Life Sciences